Method of preparing solutions of gelatin in polyhydric alcohols



Patented Feb. 5, 1952 METHOD [OF PREPARING SOLUTIONS OF GELATIN IN POLYHYDR-IG ALooHoLs Linwood F. Tice, Salem, N. J., assignor to Gela-y tin Research Society of York, N. Y.

America, Inc., New

No Drawing. Original application May 3, 1949, Serial No. 91,233. Divided-and this application November 24, 1950, Serial No. 197,507

Claims. (01. 167-82) This invention relates to the preparation of glycerinated gelatin and similar products and more particularly to certain novel methods of preparing solutions of gelatin in polyhydric alcohols. Conventional methods of preparing. solutions of gelatin in polyhydric alcohols such as glycerin involve soaking the gelatinin water, allowing the gelatin to swell therein, subsequentlyaddding glycerin, mixing the water swollen gelatin and the glycerin, heating the mixture until the gelatin dissolves in the mixture and, finally, heating the mixture at a temperature sufiicient to vaporize the water and remove it from the mixture.

A method which is only satisfactory on a small scale and only if a relatively low concentration of gelatin is employed involves heating glycerin and water to approximately 100 C. and then slowly adding granulated gelatin in divided portions with stirring until the mixture becomes when th quantity of gelatin to be dissolved is of the order of -55% of the mixture of glycerin and water. Under those conditions, the gelatin imbibes the solvent before all of the gelatin is wet. Stirring of the resulting material causes lumps of partially wetted gelatin to iorm an d entrains air in the mixture. The application of heat to the lumpy, aerated mixture does not r e sult in the desired clear,' homogeneous solution. This problem has plagued the pharmaceutical industry for years.

Solutions of quantities of gelatin in the order of approximately 30-50% by weight in glycerin desirably possess the characteristics of a somewhat plastic solid at room temperature. The ma terial dissolves in aqueous liquids andprovldes a suitable carrier for medicinal preparations in the treatment of numerous physical ailments.

The product supplied commercially by conventional methods is often of very poor quality. .So well known are the disadvantages of conventional methods that many pharmacists avoid the preparation of glycerinated gelatin whenever possible.

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2, One of the objects of-the present invention is to provide an improved method for the preparation of solutions of large amounts of gelatin in polyhydric alcohols.

Further objects will become apparent from the following description andexamples. f According to the present invention-generally stated, granulated gelatin and a polyhydricalcohol such as glycerin or propylene glycol are thoroughly chilled, for example by cooling to a temperature in the range of -5 C. to 5 C. Quantities of the glycerin or propyleneglycol are then poured over the surface of'the gelatin in proportions to provide a 30-55% concentration by weight of gelatin in the resulting mixture. A vacuum is applied to the mixture to remove residual air in the granulated gelatin, for example, by placing the mixture in a vessel to which a vacuum is applied, or by providing air-evacuating means to the gelatin in a suitable vessel such as a tube. The vacuum is applied until the glycerin has wettedall of the grains of gelatin. The mixture of gelatin and glycerin is then heated at a temperature of approximately -100 C. until the solution of the gelatin in the glycerin is complete. Occasional slow agitation without aeration may be applied to the mixture during this period. Temperatures in excess of C. tend to darken the product. The resulting solution is then cooled to room temperature whereupon it hardens to a viscous mass which can be cut into pieces for use. Medicaments canbeembodied in the solution before it cools, or'gthe cooled mass can be reheated to llquify it andthe medicaments can then be incorporated. As an alternative, the drug can be dissolved'in a snijall' quantity of water and mixed with glycerin." The mixture is then chilled, added to chilled granulated gelatin and processed in the mannerdescribed hereinabove to yield a clear, homogeneous glycerinated gelatin product. In an alternative procedure embodying the method of the present' 'i'nvention, th granulated gelatinis mixed with a primary aliphaticmonohydric alcohol such as ethyl alcohol or isopropyl alcohol, the glycerin is added and mixed thoroughly with the other ingredients and the resulting mixture is then heated to approximately 80 C. until a clear, homogeneous solution is obtained. The monohydric alcohol is then removed by evaporationor distillation. This procedure re- Example I A 500 gram quantity or" pure glycerin and a 5001,.

gram quantity of granulated gelatin in stoppered bottles were chilled by means of storage in a refrigerator at approximately C[ for :approximately four hours. The gelatin was then poured on the glycerin and the two then maintained at approximately 0 C. (within until the gela. tin was below the surface of the glycerin. The mixture was then heated in an ,oven at a torn. perature ranging from 80-100 (3. overnight. Upon cooling to room temperature, the solution solidified and became clear and homogeneous upon standing for several days.

Example II I The procedure of Example I' was repeated, using 500 grams of propylene glycol in place of the glycerin. The results were the same as in the case of Example I. Both the glycerin and the propylene glycol behaved in exactly the manner.

Example III A 50 gram quantity of granulated gelatin was lar runs were made at temperatures below 80 C.

but more time was required.

Example IV A small wad of cotton was placedin the tip of a glass funnel and 50 grams of chilled granulated gelatin was packed in the funnel above the cot ton. A vacuum line was applied to the stem of the funnel and simultaneously. therewith, 50 grams of chilled glycerin waspoured on the gelatin. When the gelatin became thoroughly wetted with the glycerin, the vacuum line was disconnected and the cotton Wad was removedf The funnel was placed in the neck of ,a bottle and both were placed in an oven at 80-100 C. After several hours, the gelatin-glycerin mass liquified and ran into the, bottle. Theliduid was then, poured into a mold'and allowed to solidify at room temperature. v

Example V A mixture of 20 cc. of water and 25 grams of glycerin was prepared and chilled to approximately 0 C. (within :5). The mixture was then added to 40 grams of chilled granulated gelatin in a flask equipped with a vacuum line as in Example III. Vacuum-was applied at once to the flask and was maintained until the-gelatin was thoroughly wetted. 'To-the resulting mass 4 was added 20 cc. of water and the mixture was placed on a water bath and heated at -100 C. for approximately three hours with occasional slow rotation of the flask. The resulting solution was then poured into molds and allowed to harden.

Example VI A mixture of grams of granulated gelatin in 60 cc. of ethyl alcohol was prepared. To this mixture was added 100 grams of glycerin. The resulting mixture was heated, the alcohol being removed by distillation until no further amounts of distillate were obtained. The residual solution was then allowed to solidify and was found to contain minor amounts of alcohol which did not interfere with the use of the product in pharmaceutical preparations.

Example VII The procedure of Example VI was repeated using 100 grams of propylene glycol in place of the glycerin. The resulting product was similar in its properties as a pharmaceutical agent with that obtained in Example VI.

' Other polyhydric alcohols may be employed in place of glycerin and propylene glycol in the improved method of the present invention, such as diethylene glycol. However, at present, the only polyhydric alcohols approved for pharmaceutical preparations are glycerin and propylene glycol. The novel process of the present invention is not limited to these polyhydric alcohols.

. This application is a division of my co-pending application, Serial No. 91,233, filed May 3, 1%9, now Patent Number 2,558,065 of which there is another copending divisional application, Serial No. 233,490, filed June 25, 1951.

I claim:

1. An improved method of preparing solutions of gelatin in polyhydric alcohols comprising chilling granulated gelatin and a polyhydric alcohol to about 0 CL, adding the gelatin to the polyhydric alcohol, allowing the mixture to stand at a temperature in the range of -5 C. to 5 C.

until the gelatin is thoroughly wetted with the alcohol, subsequently heating the mixture at approximately 80-100 C. until a clear, homogeneous liquid is obtained and thereafter cooling the liquid until a solid mass is obtained.

2. An improved method of preparing glycerin'ated gelatin comprisin gcooling granulated gelatin and glycerin to a temperature in the range of -5 C. to 5 C. adding the gelatin to the glycerin,

allowing the mixture to stand at a temperature in the range of 5 C. to 5 C. until the gelatin is thoroughly wetted with the glycerin, subsequently heating the mixture at approximately Bil-100 C. until a clear, homogeneous liquid is obtained and thereafter cooling the liquid until a solid mass is obtained.

3. An improved method of preparing a solution of gelatin in propylene glycol comprising cooling granulated gelatin and propylene glycol to a temperature in the range of -5 C to 55 adding the gelatin to the propylene glycol, allowing the mixture to stand at a temperature in the range of .-5 C. to 5 C. until the gelatin is thoroughly wetted with the propylene glycol, subsequently heating the mixture at approximately 80-100 C. until a clear, homogeneous liquid is ob tained and thereafter cooling the liquid until a solid-mass is obtained.

'4. The process as defined in claim 2 in which "the gelatin is present in the mixture in an amount 5 in the range of 30-55% by weight of the mixture. UNITED STATES PATENTS 5. The process as defined in claim 3, in which Number Name Date the gelatin is present in the mixture in an 2 6 0 1 1 9 9 amount in the range of 30-55% by weight of the E6 74 Rachel y 1 1 3 mixture 5 FOREIGN PATENTS LINWOOD F. TICE. Number Country Date 439,784 Great Britain Dec. 13, 1935 REFERENCES CITED OTHER REFERENCES i i g g gg gs are of record m the 10 Hiss and Ebert, New Standard Formulary, 5th

' 7 Ed., (1920-) pp. 394, 395. 

1. AN IMPROVED METHOD OF PREPARING SOLUTIONS OF GELATIN IN POLYHYDRIC ALCOHOLS COMPRISING CHILLING GRANULATED GELATIN AND A POLYHYDRIC ALCOHOL TO ABOUT 0* C., ADDING THE GELATIN TO THE POLYHYDRIC ALCOHOL, ALLOWING THE MIXTURE TO STAND AT A TEMPERATURE IN THE RANGE OF -5* C. TO 5* C. UNTIL THE GELATIN IS THROUGHLY WETTED WITH THE ALCOHOL, SUBSEQUENTLY HEATING THE MIXTURE AT APPROXIMATELY 80-100* C. UNTIL A CLEAR, HOMOGENEOUS LIQUID IS OBTAINED AND THEREAFTER COOLING THE LIQUID UNTIL A SOLID MASS IS OBTAINED. 